iPhone 2.0 only: My most-used app on the iPhone, Google Mobile, has a hidden settings panel called "Bells and Whistles" that lets you customize the colors and sounds. To reveal the new pane, go into Google Mobile's Settings area, scroll to the bottom of the page, and swipe up several times until the "Bells and Whistles" entry appears. Then tap it to set the app's theme color, sounds (chicken or monkey), and turn on a live waveform for voice search. Neat!